The 7D with the 100-400mm should absolutely kill at wildlife or BIFs. Don't take this the wrong way but it could be either your technique or the camera is defective. If the camera is able to take sharp pictures of still objects then it could be your technique that may need some adjustments.
I agree. I used that combo for about a year. Actually, pic #2 and #3 at the bottom of page 18 were shot with my 7D and 100-400L.